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Re: Did we break update-grub?



Hi!

Steven Chamberlain <steven@pyro.eu.org> writes:
> It can be explained by:
>
> * your zpool was already version 5000 (created by zfsutils newer than
>   that in wheezy), having feature@lz4_compress "enabled", but it wasn't
>   "active"/in use yet (see `zpool get all`)
>
> * you started using kFreeBSD 10.1, which if feature@lz4_compress is
>   enabled, will compress new metadata with lz4 compression (which is
>   unrelated to the zpool 'compression' setting for file contents)
>
> * GRUB << 2.02 can't understand lz4, grub-probe returns "unknown"
>   filesystem type and it's not handled very robustly here

That would indeed explain it!

> This seems like a rare situation.  Normally an upgrade from wheezy
> or current jessie to sid would have:
>
> * zpool version 28 with no feature@lz4_compress, so kFreeBSD 10.1
>   can't make lz4 active in the pool unless they did a manual
>   `zpool upgrade`
>
> * kernel upgraded together with grub-pc (>= 2.02~), which supports
>   using lz4 in a zpool
>
> I see this perhaps being a problem if 10.1 migrates before grub-pc
> does.

Which looks like it will be the case -- grub2 currently introduces new
bugs and probably can't migrate without another upload which would put
it behind kfreebsd-10 timing wise. I guess we could ask release to block
it maybe.

Also I think it's fine installing kfreebsd-10 10.1 on jessie and using
that as long as you don't upgrade the kernel while running a 10.1 so the
upgrade case should be fine right (grub will understand all needed
metadata for booting the kernel if installing it was done on 10.0)?
I'd still set a breaks on lower grub-pc on the next kernel update or
something like that.

> Or, trying to install a jessie system from sid d-i.
> What we could do is set feature@lz4_compress=disabled in partman-zfs,
> just temporarily, until the newer grub version migrates.

Not sure how much work that is. If it's quick and easy I'd go for it.

  Christoph

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